We investigate the evaporation of water molecules from the surface of high index, amorphous thin TiO2 films of various thicknesses t(t), grown by atomic layer deposition (ALD). The desorption of water molecules is impeded by depositing thin ALD-Al2O3 barrier layers of various thicknesses on the TiO2 thin films. Growing ALD-Al2O3 diffusion barrier layers with different thicknesses t(a) allows us to evaluate the water vapor evaporation rate in terms of the change in the thermo-optic coefficient (TOC) of TiO2 films over a wide spectral range 380 <= lambda <= 1800 nm. An average reduction of 33% in TOC is found at a barrier layer thickness of similar to 36 nm. Furthermore, the temperature dependent index (dn/dT) and density (d rho/dT) of the ALD-Al2O3 films of various thicknesses t(a) are also presented. The Cauchy model is applied to all the ellipsometric measurement data to retrieve the optical constants, and subsequent modeling by the Lorentz-Lorenz relation provides the material density of Al2O3 films. The room temperature values of the thermal coefficients for an ALD-Al2O3 film of thickness t(a) approximate to 60 nm at wavelength lambda = 640 nm are found to be dn/dT = 4.66 x 10(-5)degrees C-1 and d rho/dT = 4.66 x 10(-4)g cm(-3)C(-1). (C) 2013 Elsevier B.V. All rights reserved.